Heart arrhythmia, also known as cardiac dysrhythmia or irregular heartbeat, is a group of conditions in which the heartbeat is irregular, too fast, or too slow. While most types of arrhythmia are not serious, some predispose a person to complications such as stroke or heart failure. Others may result in cardiac arrest. For example, Atrial Fibrillation (AFib) is one of the most common cardiac arrhythmia and the presence of AFib could potentially lead to major health risks. Traditionally, heart arrhythmia is detected by electrocardiogram (ECG) or a Hotler monitor.
ECG measurements require sophisticated detection device with multiple electrodes attached to the patient and require active human participation. Typically, ECG measurements are taken only for diagnostic purpose after the patient become symptomatic. Photoplethysmogram (PPG) has been described as an alternative to ECG in arrhythmia detection. However, some conventional PPG measurement technique for heart arrhythmia relies primarily on heart beat or heart rate detection using an average heart rate, such as a window between 5 and 20 seconds. Average heart rate variation by itself is not a reliable sign for arrhythmia.
Other PPG based methods for detecting heart arrhythmia suffer from low sensitivity and specificity. Also, some methods require a large continuous chunk of PPG signal, such as 30 seconds of continuous PPG signal to effectuate the measurement.